Hurricane Florence Looks A Lot Like Harvey With One Key Difference: Geography

Meteorologists are warning that Hurricane Florence could be the "Harvey of the east coast," dumping record rains and triggering unprecedented flooding. While the two hurricanes may be similar, the geography of the Texas gulf coast and the Carolinas is quite different.

Hurricane Harvey made landfall in Texas in August of 2017 and from there stalled over the Houston metro area for five days, dumping upwards of five feet of rain on a city built on swamplands. The 60 inches of rain simply didn't have anywhere to go as the hurricane sat over Houston, continually feeding water from the gulf onto Houston.

Hurricane Florence forecasted model.tropicaltidbits.com

The scenario for Hurricane Florence is a similar one, meteorologists are extremely worried about a ridge of high-pressure sitting just off the coast of New England. What this high-pressure system will do is prevent Hurricane Florence from veering off toward New England and back out to sea. It will act as a wall, holding the hurricane in place for days over North Carolina.

As Hurricane Florence makes landfall, the winds will die down but the rain will continue to fall. Much like Hurricane Harvey, Florence is looking like a prolonged deluge of rain over North Carolina. To add to the severity, the Carolinas have received several inches of rain recently, making the soil saturated and increasing the likelihood of runoff. This will put millions in the southeast at risk of flooding, combined with potential 12-foot storm surges on the NC coast, this could be one of the worst flooding events in NC history.

Forecasted rainfall from Hurricane Florence.NHC

The Scary Difference Between Harvey and Florence: Geography

What were weeks of standstill flooding in Houston will be rapidly flowing flash flooding rivers in NC. The key difference is geography and the presence/lack of barrier islands.

North Carolina's chain of barrier islands which run off the coast of the state act as literal barriers during hurricanes such as Florence. The brunt of the waves and storm surge from Hurricane Florence will hit the fragile barrier islands, causing step changes in their structure and literally pushing the islands landward. However, this will act to protect the NC mainland from the open seas, dampening the storm waves and surge.

A flooded road on Hatteras Island, N.C., after Hurricane Irene, swept through the area the previous day cutting the roadway in five locations. (AP Photo/Jim R. Bounds)

Compare this with Harvey, which took the full brunt of the storm without dampening. This is good news for those living on the NC mainland as the state has natural "seawalls" to protect it. This comes as a cost for those living on the barrier islands or have vacation homes on the fragile islands.

The second key difference is the topography of NC versus Texas. Houston is built on what would be swamplands, with flat terrain that stretches on for hundreds of miles. This means when record amounts of rainfall, gravity doesn't help it flow to the sea. With downtown Houston 50 miles from the coastline and just 50 feet above sea level, the water simply stalled with no place to run off. Compare this with Raleigh, NC, which sits at 315 feet elevation and is 100 miles from the coastline. The slope from Raleigh to the coast compared to Houston to the coast is 3 times higher.

Elevation map of NChttp://topocreator.com

Add the Appalachian Mountains into the mix and what NC will likely encounter are rapidly moving rivers, overflowing their banks and washing debris and property downstream. Where Houston battled standstill waters for weeks, NC will battle uncontrollable rapids running through cities and towns.

I am a geologist passionate about sharing Earth's intricacies with you. I received my PhD from Duke University where I studied the geology and climate of the Amazon. I am the founder of Science Trends, a leading source of science news and analysis on everything from climate...